In recent years, vehicle GPS devices have grown in popularity and are now widely available in a variety of forms, including different types of In-Vehicle Navigation Systems (IVNSs). These systems are primarily based on a Global Positioning System (GPS) which was founded by the U.S. Department of Defense and consists of a constellation of twenty-four satellites working in conjunction with five base stations. The satellites orbit the Earth and transmit precise timing data to GPS receivers located on Earth. If strong signals from three or more satellites are received, then a latitude and longitude (two-dimensional) position can be determined; if strong signals from four or more satellites are received, then a latitude, longitude and altitude (three-dimensional) position can be calculated.
In addition to providing an occupant with navigation-related information, the IVNS can also transmit important vehicle position information during an emergency call. Telecommunication companies have successfully implemented enhanced 911 (E911) services throughout the country, giving the public fast and easy access to a Public Safety Answering Point (PSAP) which is in turn connected to various local emergency responders. E911 systems automatically send certain information such as the caller's location to the PSAP so that it can dispatch emergency services to the caller's location without requiring the possibly panicked caller to convey their location. Traditional land-line telephone systems utilize the telecommunication company's records to lookup an address based upon the caller's phone number. However, this technique does not provide meaningful location information for E911 calls originating from a wireless telecommunication system, such as an IVNS or a mobile phone.
Therefore, in order to enable E911 systems to obtain quick and accurate information during an emergency wireless call, the federal government enacted wireless E911 rules. One of the purposes of the new E911 rules is to enable the PSAP to obtain as much helpful information as possible during an emergency call originating from a wireless INVS; particularly, information relating to the current position of the vehicle.